The Future of Frogs in Danger

It is not easy to predict the impact of rapidly increasing human populations and activities on natural ecosystems. Now, we are facing a fungal disease affecting frogs. A fungus called Batrachochytrium dendrobatidis (Bd) managed to achieve the record of a documented, pathogen-induced loss of biodiversity. (Cats and rodents are the next on the list.)

Bd emerged in Asia in the 1980s, spreading through live animal trade, causing mass deaths even in untouched natural environments. At that time, the pathogen was not identified. It threatened more than 500 amphibian (animals with life cycles involving both water and land habitats) species, 90 of which are estimated to become extinct, while the population of 124 fell below 10 percent. Meaning, Bd deserves its rightful place in the list of “most harmful invasive species”.

The disease caused by Bd is called chytridiomycosis. Among amphibian species, it affects frogs the most, because of the unique structure of the frog skin. Frog skin has thin and permeable, enabling them to breathe through it, quench their thirst, and maintain the body’s salt balance. That is, there is a constant fluid exchange through the skin. Bd settles on the skin of mature frogs, disrupts fluid exchange, and causes heart failure within a few weeks. Larger species that are slow-growing (which reach the age of reproductive maturity later), more isolated, living in higher altitudes with limited habitat options, especially living in wetlands where fungus likes and spreads its spores more easily are in greater danger.

Ecologist Ben Scheele from the Australian National University in Canberra conducted a comprehensive study with 40 other researchers in order to examine the health and population status of frogs worldwide. According to new figures, 12 percent of the 292 frog species that have a known population trend is recovering. Places, where the pathogen does the most damage, are Australia, Central, and South America. Islands with high biodiversity such as Madagascar and Papua New Guinea are clean for the moment, though they carry a great risk.

Frogs make up 6.5 percent of all known amphibian species.

The fact that a single disease threatens an entire vertebrate class is quite serious. It is also daunting to see how global trade routes play a role in spreading diseases by breaking natural dispersion borders.

With the help of such studies, we learn more about how we can protect and conserve frog species. First, it is clearly and obviously a must to restrict live animal trade. In places with sensitive and fragile ecological balances, such as Australia, living creatures entering and exiting the country are under strict monitoring. However, we do not know how our interventions will affect long-term natural balances, unfortunately.